The invention relates to the production of photovoltaic cells, particularly for converting solar energy into electricity. Such cells often have a structure that is a stack of thin films, with at least one of these thin films having photovoltaic properties. The invention relates in particular to preparing and obtaining this photovoltaic film, referred to below as the “absorber”.
The absorber is prepared here by electrodeposition. It is based on an alloy formed of elements of group I (such as copper), III (such as indium and/or gallium and/or aluminum), and VI (such as sulfur and/or selenium). Such an alloy, having an overall stoichiometry of close to I-III-VI2, is known to offer good photovoltaic properties.
In the technique of the present application, a solid I-III alloy is first formed by electrodeposition and element VI is then added by annealing in an atmosphere rich in element VI. In practice, two electrodes with a voltage differential applied to them are immersed in an electrolysis bath containing appropriate salts (for example compounds based on copper, indium or gallium as will be further discussed below), and the deposit is formed on one of the electrodes.
However, often the I-III alloy has local compositional inhomogeneities relative to the deposition in general, as well as irregularities in shape (cavities, interface irregularities, etc.). In addition, these defects remain present in the final layer after the element VI is added and the photovoltaic conversion efficiency is affected.
The invention improves the situation.